The present invention relates to the washing; decontamination and sterilization arts. It finds particular application in conjunction with cleaning apparatus for medical, dental, surgical veterinary, and other devices and equipment and will be discussed with particular reference thereto. It is to be appreciated, however, that the invention is also applicable to washing, decontaminating or sterilizing devices and equipment in other fields.
Reusability of medical devices is becoming increasingly important in an effort to provide cost effective health care. Traditionally, the effectiveness of processes for cleaning medical equipment has been assessed by measuring the ability of the process to sterilize the processed items. Frequently, a biological or chemical indicator is included with the process load. After completion of the process cycle, the indicator is evaluated to give a measure of the effectiveness of the cycle in terms of an estimation of the likelihood that microorganisms present in the load have been destroyed.
Recently, it has been shown that for many purposes, killing efficiency is not a complete measure of the decontamination process. Non-living, organic contamination may remain on the apparatus which is not detected by chemical and biological indicators. This contamination, known as soil, includes biological materials such as dried blood, mucous, feces, saliva, and bile. This soil can compromise the efficient use of the device or inhibit its sterilization and lead to infections when the equipment is reused. In particular, microorganisms that have been destroyed in the decontamination process, but which remain on the surfaces of the apparatus, can be a health hazard. The dead remains of those microorganisms degrade to form products which are harmful to humans. For example, the walls of Gram negative bacteria degrade to form endotoxins which can cause pyrogenic reactions in patients with which the equipment is used.
In addition, materials such as blood and other medical wastes, which remain on medical equipment, provide sites which encourage microorganisms to grow. Further, if the soil is not thoroughly removed during the cleaning process, it may become fixed to the surface of the apparatus in such a manner that makes future cleaning difficult if not impossible. For example, glutaraldehyde solutions, used for the disinfection of medical devices, have been shown to create a layer of cross-linked soil on endoscopes which proves to be highly resistant to removal. Robert C. Tucker, Brian J. Lestini & Roger E. Marchant, ASAIO J. Vol. 42, No. 4 (1996) p. 306. Residual soil also hinders the ability of subsequent sterilization or disinfection processes to destroy infectious microorganisms by insulating the organisms from the sterilant or disinfectant and impeding penetration.
In one technique to assess the ability of a cleaning process to remove soils, two metal plates are soiled, clipped together, and subjected to the cleaning cycle. Removal of the soil is an indication that the cleaning process has been effective. A protrusion on one end of one of the plates creates a variably sized crevice between the plates when the two are sandwiched together. This could allow an estimate of the degree of cleaning if the soil is removed from only a portion of the crevice, usually the wider part.
Although the metal plate method gives an indication of the effectiveness of cleaning, it may not simulate the more challenging examples of medical equipment requiring cleaning, such as endoscopes. Medical equipment currently in use often contains designs, which readily absorb medical soils and do not release them easily during the cleaning process. Moreover, although a rough assessment of the effectiveness of cleaning may be made visually, the method is not readily amenable to accurate assessment of the extent of soil remaining.
The present invention provides a new and improved apparatus and method for testing the effectiveness of soil removal which overcomes the above referenced problems and others. The method may be used both for process validation testing and for periodic testing of the cleaning apparatus in use.